Evil is not a complex philosophical concept. It is very easy to understand if you look at it from a purely phenomenological point of view: any thing or person who deliberately stops you from accomplishing your goal or purpose in life is evil.

If you can't understand this most basic idea, then I would argue you don't know what your purpose in life is, or you have never overcome serious obstacles in life.

So the 'logical evidence-based root cause of evil' is a relationship between the subject and goal, with evil being the person or event that stops the subject from reaching their goal. The worse the relationship, the greater the evil.